What keeps self adjusting shoes from winding up too tight?

[Moparfiend]

Was wondering how the auto adjuster works on my rear brakes and what keeps the adjuster from getting too tight?
I am talking about the rear drums on my 1970. They are new and after setting them by hand and not having any binding I did some reverse drives and applied the brakes to snug them up.
BUT my right rear drum was smoking when I got back. Trying to figure out what happened. My first question is if I didn’t tighten them by hand manually and how did they get so tight? my second question was what prevents the adjuster from making them too tight and why only that wheel?

So what prevents the auto adjuster from making them too tight?

 

[Moparfiend]

By the way, I just rebuilt these so everything‘s new including the cylinder. They are the original drums they were good shape. This is what they look like after test drive. The adjuster runs smooth.

 

[zyzzyx]

The adjuster lever needs to travel a certain amount to "Bite" the next tooth on the adjuster wheel. If it can't reach the next tooth,
then the adjuster doesn't turn and no tightening occurs. When the brake shoes wear just enough so the lever can grab the next
tooth, you have automatic adjustment!

 

[sam dupont]

No parts can flex or bend allowing one click too many?

 

[Moparfiend]

The adjuster lever needs to travel a certain amount to "Bite" the next tooth on the adjuster wheel. If it can't reach the next tooth,
then the adjuster doesn't turn and no tightening occurs. When the brake shoes wear just enough so the lever can grab the next
tooth, you have automatic adjustment!

Could this be a proportional/ hydraulic issue?I thought for sure the drum wouldn’t come off or at least without a fight but it came off surprisingly easily.

 

[Don Frelier]

If the drums have no ridge between the shoe and the outer edge I can almost always get them off without a brake spoon.
Almost always occasionally I need a spoon.

 

[twecomm]

Im looking at the first pic and it appears that there is some slack in the adjuster's cable. Is the other side like that ?

 

[1 Wild R/T]

Sorry to be so blunt but those shoes are junk... The linings are bonded to the wrong area of the shoe... Look how low on the shoe that front lining is... It's a known issue with current replacement shoes.... It will cause the shoe web to flex, it also will cause the self energizing effect of drum brakes to not work properly....

 

[Mopar Miki]

emergency brake adjustment, as to the junk linings - seems to be the norm, no one wants to use modern lining materials that work

 

[Cranky]

My driveway is over 100 feet long and the wife would back up way too fast and then stomp on the brake to a stop dead and then look to see if anyone was coming down the road. Well, that kept the rear drums tight and they wore out fast. Solution? Disconnect the damn adjusters and usually did that to all of my vehicles. When the pedal travel was a bit more than normal, I'd adjust them by hand which was usually 3rd or 4th oil change. The wife's car though.....adjusted them every oil change! She was extremely hard on cars. I found many moons ago that the adjusters can over tighten so backing up at a slow rate and not lean on the brake very hard was the best way to make the linings last. This was even on cars that were fairly new back in the day.

 

[1STMP]

I wouldn't trust any brake linings on any set of brake
shoes to match the radius of the drum they're being
installed into. NAPA used to match grind the linings
to insure full contact with your drums and would
label the shoes as to their prospective mounting
locations. I don't think they'll do this any longer unless
it's requested.
Your adjusters may be over compensating for high spots
on the shoe linings.

 

[twecomm]

Start with quality brake shoes & drums. And yes, it would be nice if you could still find folks to arc the shoes to match drums as described above. However, If you have new drums, I start by having my local parts shop turn the drums and shave em' just enough to make sure they are perfectly in round. I will manually adjust the brakes and do some test drives and tweak the adjusters so brakes feel well balanced front to back and side to side. I'll get some easy braking mileage on the shoes so they get broken in and properly conform to the drums. A final check and tweek of adjusters if needed and let the self adjusters handle it from there.